Phase control system



J. PLEBANSKI PHASE CONTROL SYSTEM Sept. 5, 1939.

Filed March 30, 1937 AMPLIFIER 2 I AMPLIFIER maven 0 QM in cohr sin col cup! AMPLIFIER MODULATOR AMPLI FIE R MODULATOR -4 Basin d- Bcog t 'u INVENTOR. slebanski Patented Sept. 5, 1939 PHASE CONTROL SYSTEM Jozef Plebanski, Warsaw, Poland, assignor to i 7 Radio Patents Corporation, New York, N. Y., a

corporation of New York Application March 30, 1937, Serial No. 133,793

' In Poland September 17, 1936 22 Claims. (Cl. 179-171.5)

microphone according to the invention with final The present invention relates to electrical circuits, more particularly to alternating current circuits, and among the objects of the invention are the: provision of means .for and a method of varying and controlling the phase of an alternating current such as a high frequency current in a radio circuit or the like.

' A more specific object of the invention is the provision of a system of and a methodfor converting alternating currents, more particularly radio frequency currents of varyingamplitude into currents of varying phase.

-A'fu'rther object is to provide an arrangement for converting alternating currents having different amplitudes into currents of substantially the same amplitude and relative phase difference proportional to the initial amplitude relation.

Another object is the provision of a system for and a method of obtaining a combined amplitude and phase modulation of two mutually modulated alternating currents which may be recombined into pure amplitude modulated currents to increase the efliciency' of modulation.

A further objectis theprovision of a system for and a method of producing single side band modulated carrier. signals with or without suppression of the carrier, wherein either of the side bands may be selected as desired in an easy and simple manner.

Still a further object is the provision of a simple: and efficient device and a circuit and method of operating therefor for eifecting phase modulation of a carrier current with or without subsequent conversion of the phase modulated carrier into pure amplitude modulated carrier.

The above and further objects and advantages of the invention will become more. apparent from the following detailed description taken with reference to the accompanying drawing illustrating several practical exemplifications of the invention.

In, the drawing wherein like reference characters identify parts of like function throughout the different views thereof,

Figure 1 illustrates a phase modulating system according to th'e'invention for use in a wireless transmitter or the like with final recombination of the phase modulated carrier current into an amplitude modulated carrier.

Figures 2 to 5 are theoretical diagrams explanatory ofv the function and operation of the system according to. Figure 1.

Figure 6- illustrates a single side band. transmission system embodying the principle of the invention. j

Figure-7 illustrates the invention as embodied in a high frequency microphone device for effecting a phase modulation.

Figure 8: illustrates acomplete modulating circuit embodying a phase modulating device or co'nversionof the phase modulated carrierlcurrent into an amplitudemodulated carrier.

Figure 9 is a diagram explanatory of the function of the circuit of Figure 8.

With the above objects'in view, the invention generally involves a method for combining or reacting upon one another alternating currents through a circuit arrangement comprising substantially a pair of coupled resonant circuits simultaneously excited by potentials of like frequency which may be supplied from a common source of oscillation or carrier current generator. The circuits are separately tuned to resonance with the exciting current and v then coupled together inductively or in any; other suitable manner.

wherein I1 and I: represent the amplitudes of the currents in the respective circuits,

o1 and 2 thephases of the respective currents,

E1 and E2 the electromotive forces impressed upon the circuits, f w

R1 and R2 the loss of non-reactive impedances of the circuits,

L1 and L2 the valuesof the self inductances of the circuits, I

C1 and C2 the values of the capacities of the circuits;

M the coefiicient of the mutual induction or I coupling between the circuits, o the phase diflerence between the currents in the circuits. l W= f with 1 representing the frequency of the currents and 1 ,1, 1 **w c1)( rve)- From the above equations'it follows that the phases of the currents and also their amplitudes tude and phase modulation for improving the cordance with the modulating signal variations.

as a vacuum tube oscillator.

operating conditions and efficiency of the system. Phase modulating arrangements of this type known in the art usually comprise means for generating a carrier current of constant amplitude, the phase of which is changed in ac- Alternatively, both phase and amplitude may be varied simultaneously. The latter system has great use for wireless transmitters in order to improve the overall energy conversion efficiency of the system. In known arrangements of this type, usually two amplifying channels are provided fed with separate carrier components the phase difference between which is varied in accordance with the variations of modulating signals. The phase modulated currents are then recombined in a common output or utilization circuit to produce a resultant amplitude modulated current.

In the drawing, details of parts not necessary for an understanding of the invention have been indicated schematically only to simplify the description and drawing.

The system according to Figure 1 comprises a driver shown at l which may be any known type of high frequency oscillator or generator such The carrier current supplied by the driver is divided into two components each of which is transmitted through a separate amplifying branch or channel. The outputs of the amplifying channels in the example shown are recombined in a common utilization circuit. In the example illustrated, the first channel comprises a pre-amplifier having a final amplifying stage I5. The amplified carrier currents supplied by the latter are impressed through a coupling condenser l1 upon a resonant circuit comprised of a capacity l9 and inductances 20, 2| in parallel. This resonant circuit is coupled with the grid of a final amplifier stage or tube 21 by means of a pair of coupling condensers 25 and 30 and a grid leak resistance 32 in a manner well known in the art.

Similarly, the second channel comprises a preamplifier |2 which in the example shown serves also as a modulator and'has a final amplifying stage represented by the amplifying tube IS. The modulating currents may be supplied from any suitable source such as a microphone to be connected at M and are impressed upon the amplifier or modulator |2 of the carrier suppression type through a low frequency transformer l3. The modulation may be affected in accordance with any one of the known methods such as by varying the grid or anode potential of a modulating tube in the amplifier l2. Furthermore, the

suppression of the carrier may be obtained by using any one of the known systems such as a balanced modulating circuit well known in the art, the modulation per se forming no part of the present invention. The amplified modulated signals supplied by the tube l6 are impressed through acoupiing condenser l8 upon a second resonant circuit comprised of a capacity 22 and inductances 23. 24 in parallel. -Both resonant circuits I9, 20, 2| and 22, 23, 24 are shown to be coupled inductively through the pair of coupling coils 2| and 24 arranged in inductive coupling relation, the former being connected in series with the inductance 20 and the latter in series with the inductance 23. The resonant circuit 22, 23, 24 is coupled to the grid'of final amplifying tube 28 by means of condensers 26 and 3| and grid leak -33 in a manner similar to the circuit I9, 20, 2|. The output circuits of the tubes 21 and 28 are connected in push-pull by the aid of v a transformer having a primary 36 with a center tap connection leading to the positive pole of a common high tension source indicated by the sign, and a secondary 31 shunted by a tuning condenser 38 and forming the output circuit which may be directly connected to a utilization circuit such as an antenna or the like.

In the above equations R1 represents the ohmic impedances of the circuit I9, 20, 2| and R2 represents the ohmic impedance of the circuit 22, 23,

24; C1 corresponds to the capacity I 9, and C2 to the capacity 22; L1 corresponds to the inductances 20, 2| and L2 to the inductances 23, 24 while M is the inductive coupling coefficient between coils Supposing that the circuit'l9, 20 and 2| is excited by an electromotive force A sin wt from the valve l5 and that the circuit 22, Hand 24 is disconnected from valve l6 and therefore has no potential impressed on it. It will then be found from the above equations that the vectors of the currents in both circuits are in phase-quadrature as shown at a and b in Figure 2. Since the circuits I9, 20, 2| and 22, 23, 24 excite the tubes 21 and 28 respectively, the outputs of which are connected in push-pull arrangement, a combined carrier will appear in the common output circuit 31, 38 having a phase and amplitude equal to 0A as shown in Figure 2, that is, equal to the vector sum of the currents I1 and 1: represented by a .and b.

If a modulated current in which the carrier has been previously suppressed as represented by B sin. wt sin pi and obtained in any known manner such as by means of a balanced modulator or the like, is then impressed upon the circuit 22, 23, 24 it is found by analysis from the above Equations I and II that the vectors a and I) representing the currents become phase modulated such as illustrated by the diagram of Figure 3. In the latter, the ends of the carrier vectors a and b move along lines (1 and c in accordance with the variations of the modulating signals. In the output circuits 31 and 38, a pure amplitude modulated current is obtained as illustrated by the vectors 0B, 00', 0A. In case of a 100% modulation, the diagram will be as shown in Figure 4. If the constants of the circuits are not exactly equal, that is, if R1, R2 and 10M are not alike, then the phase diagram will assume a form as shown in Figure 5 from which it follows that the amplitude modulation in the output current will be proportionate to the original modulating current without. any distortion or spurious phase modulation.

The-operation and adjustment of the system described is as follows. At first, the modulation in the amplifier I2 is interrupted and both circuits I9, 20. 2| and 22,23, 24 are exactly tuned to resonance with a very weak coupling between them. After the circuitshave been tuned, the coupling is increased until the measuring instruments and 35 connected across the condensers 30 and 3|. respectively show an equal deflection. After this has been done, both circuits are tuned and the couplingimpedanceis equal to the ohmic impedances of the circuit provided the latter are designed to have substantially equal values. The

vector diagram for. this condition is shown in Figure 2. The modulating currents are then impressed through the transformer I I3 whereupon the 'sy'stemwill operate in'the manner described. From the above it is seen that mutual phase modulation between two or more carrier currents is accomplished in a most simple and emcient manner by means of a phase splitting or twin a high frequency oscillator of any known type from which are derived two carrier components which are passed through separate modulating.

and amplifying channels and impressed upon a common output circuit. The first channel shown comprises a modulator and amplifier 40 having a final stage 46-from'which the modulated currents are impressed though a coupling condenser 48 upon one'of a pair of phase spreading or twin circuits of the type according ,to the invention comprising a condenser '58 and an inductance in parallel and'a coupling coil 52 in series with the latter. The second channel comprises a modulator and amplifier 4| having a final stage 41 from which the modulated currents are impressed through a coupling condenser 49 upon the other phase spreading or twin circuit comprising a condenser 53 in parallel with an inductance 54 and a coupling coil 55 in series with the latter. The coils 52 and 55 are arranged in inductive relation in a manner similar as shown in the previous figures. Either of the twin circuits 50, 5| and 52 or 53, 54 and 55 may be connected to the input of a common output amplifier 62 by means of a switch 56 through coupling condensers 51 and 58 and a grid leak resistance 59 similar as described in connection with Figure 1. of the amplifier 62 includes a timed transformer having a primary 53 and a secondary 64 shunted by a tuning condenser 65. The output circuit 64, 65 may be connected to a utilization circuit such as an antenna or the like.

The arrangement difiers from that shown in Figure 1 by the factthat both carrier components supplied by the driver w are modulated by components in phase quadrature of the same modulating signal.

modulator 4| is connected to a modulating circuit,

Thus, in the example shown, the

plied to the modulator 4|. Such modulating cur rentcomponents in phase quadrature may be secured in. accordance with any one of the well known methods in the art not shown for sake of The output circuit the stationary coil 1|,

in accordance with one known method, an initial modulating current is employed tomodulate an auxiliary carrier frequency wave from which one side band is eliminated such as by means'of filters .or. any other known arrangement. Theremaining side band. is then combined with a: new car- 'rier' phase shifted relative'to the initial carrier and the resultant current then demodulated.

In this manner, a modulating current is obtained which is 90 phase shifted relative to or in quadrature with the original modulating current. If desired, the carrier may be suppressed by using any one of the known means therefor, such as balanced modulators wherebyeither the simplicity of the description and drawing. Thus,

upper or lower side band alone is obtained in the output of the system.

By modulating the separate carrier'components in accordance with the quadrature modulating currents as described corresponding carrier potentials are impressed upon the twin or phase spreading circuits 50, 5|, 52and 53, 54, 55.

Theoretically, the impressed potentials are repre- ,sented by the following formulae as indicated in the drawing: A sin wt 4- B sin wt sin pt impressed upon circuit 50, 5|, 52 and A sin wt B sin wt cos pt impressed upon circuit 53,-54, '55.

By analysis and development of the above Equations I and II, it can be shown that in both circuits 50, 5|, 52 and 53, 54, 55 one of the side bands will be suppressed, i. e., if in one of the circuits the upper side band is eliminated the I v lower side band will disappear in the other cir cult and vice versa. In this mannerby placing switch 56 in either of the two positions, it is possible to select'either the upper or lower modu lation side band to be applied'to the output circuit 64 and 65. As isunderstood the above applies to any modulating signal varying in accordance with a complex function which may be inductance coil II is fed from a high frequency source such as an oscillator shown at 12 in series with a tuning condenser 10. A pair of" crossed coils 13 and 14 fixed relatively to each other are arranged to rotate about a common axis within The coils l3 and 14 are connected to a diaphragm i5 through a connecting member 16 having one end thereof secured to the common shaft of the coils and having its opposite end supported in a resilient mounting. Thus, the movements of the diaphragm 15 caused by sound variations impinged upon the same are transmitted to the crossed coils i3 and 14 which latter oscillate about their axis in accordance coils F3 and 74 are each shunted by a tuning condenser Ti and i8 respectively in series with coupling coils 19 and 80, the latter-being arranged in inductive coupling relation to form a pair of phase spreading coupled circuits similar as described Thus, if the constants of the twin'circuits are chosen in a manner described hereinabove (R1=Ra=wM) carrier currents of substantially equal mplitude but relative phase shift in accordan e with the modulating signal variations are supplied at the output terminals of the twin circuits. As is understood, the coils l3 and 14 may be arranged in fixed position and coil 1| oscillated by the diaphragm I5 to secure the same efiect. This function is further illustrated by the diagram in Figure 9 wherein the vectors 0A, 0A and 0A" represent the current in one of the twin circuits and the vectors 8B, 8B 8B" represent the current in the other twin circuit. The vectors 0A and 8B correspond to the normal condition from which position the vectors move or spread to the left or right in both directions (A, A" or B, B"

respectively) in accordance with the variations" of the modulating magnitude such as the sounds impinged upon the diaphragm I5 in the example illustrated. As is understood the vibratory. movement may be imparted tothe crossed coils or the stationary coil, respectively by any other suitable drive or pick-up system in place of the diaphragm as illustrated.

Referring to Figure 8, there-is shown a complete phase modulating system embodying a modulating device similar to Figure 7. The latter comprises a pair of coaxial movable coils 8| and 82 carried by the diaphragm l5 and both connected in series and fed from the driver 88. Item 85 is a tuning condenser shunted across both coils 8| and 82. The twin or phase spreading circuits are comprised of a pair of fixed inductance coils 83 and 84 shunted by tuning condensers I1 and I8 in series with coupling coils I9 and 80 arranged in inductive relation with each other. The inductancecoil ofone of the twin circuits 83. is arranged in inductive coupling relation with one of the movable coils 8| operated by the diaphragm l5 and the inductance coil of the other. twin circuit 84 is arranged in inductive relation with the other coil 82 operated by the diaphragm. Thus, if sound waves are impinged upon the diaphragm [5, it is seen that the coils8| and 82 carried by the latter will move, in an axial direction in such a manner that one of the 'coils will approach the associated coil of its twin circuit while the other coil willmove away from the coil ofits associated twin circuit whereby similarly as in Figure, '7 currents having an amplitude diiierential corresponding to the modulating variations are impressed upon the twin circuits and are transformed into phase modulated currents in the latter in the manner described before. The phase modulated currents are then further am-' plified preferably by separate amplifiers of which the input stages have been shown at 81 and 88 and may be recombined by means of a push-pull transformer having a primary 89 for utilization in the common output circuit formed by the secondary 90 and tuning condenser 9| in parallel therewith. The use of separate amplifiers for the phase modulated signals prior to their recombination and into amplitude modulated currents has the advantage of greater stability and increased efficiency in the final amplifying stages compared with a commonamplifier for the recombined current. 1

It will be evident from the above that the invention is susceptible of numerous variations and modifications difiering from the specific arrange ment of parts and methods of operation shown by the above d s r bed e m i at qasa d o ing within the broader scope and-spirit of the invention as, defined in the appended claims. It is intended accordingly that the specification is to be regarded in an illustrative rather than a limited sense.

I claim: I I

1. In combination, a pair 01' resonant circuits tuned to substantially the same frequency, a coupling element interconnecting said circuits, the

non-reactive impedances of said circuits being substantially equal to one another and to the mutual couplingimpedance therebetween, means for impressing potential components of resonant frequency upon said circuits, and furthcrmeans for varying the amplitude of at least one of the impressed components to effect a corresponding phase shift between the currents developed in I said circuits. l

2. In aphase modulating system, a source of carrier oscillations, .a pair of resonant circuits tuned to the frequency of said oscillations, means for impressing carrier potential components from said source upon said circuitaa coupling element interconnecting said circuits, the non-reactive impedances of said circuits being substantially equal to one another and to the mutual coupling impedance therebetween, and means for varying the amplitude of at least one of the impressed carrier components in accordance with variations of a modulating signal magnitude.

3. In a modulating system, a source of carrier oscillations, a pair of resonant circuits tuned to the frequency of said oscillations, means for impressing carrier potential components from said source upon said circuits, an inductive coupling device interlinking said-circuits, the non-reactive impedances of said circuits being substantially equal to one another and to the mutual inductance therebetween, means for varying the amplitude of at least one of the impressed components in accordance with variations of a modulating signal magnitude, and means for combining the currents developed in said circuits.

4. In a modulating system, a source of carrier oscillations, a pair of resonant circuits tuned to the frequency or said oscillations, each of said circuits comprising an inductance and a capacity element in parallel, additional coupling coils in said circuits arranged in inductive coupling relation, means'for impressing carrier potential components from said source'upon said circuits, the non-reactive impedances of said circuits being substantially equal to one another and to the mutual coupling inductance therebetween, and means -.for varying the amplitude of at least one of said impressed components in accordance with variations of a modulating signal magnitude.

5. In combination, a source of carrier oscillations, a pair 01' resonant circuits each tuned to the frequency of said oscillations, means for impressing carrier potential components from said source upon said circuits, a coupling element interconnecting said circuits, the non-reactive impedances of said circuits being substantially equal to one anotherand to the mutual coupling impedance therebetween, and means for varying the amplitude'of at least one of the impressed components to effect a corresponding phase shift between the currents developed in said circuits.

6. In combination, a source of carrier oscillations, a pair of resonant circuits tuned to the frequency of said oscillations, each of said circuits comprising an inductance coil and a condenser in parallel, coupling coils included in said cults being substantially equal to one another resonant circuits and arranged in inductive couplingrelation with each other, the non-reactive impedances of said circuits being substantially equal to one another and to the mutual coupling inductance between the circuits, and means for varying the amplitude of at least oneof the impressed potentials to effect a corresponding phase shift between the currents developed in said resonant circuits.

'7. In combination, a source of carrier oscillations, a pair of resonant circuits tuned to the frequency of said oscillations, each of said circuits comprising an inductance coil and a condenser in parallel, said resonant circuits being arranged in mutual coupling relation, the non-reactive impedances of said circuits being substantially equal to one another and to the mutual coupling impedance between the circuits, means for varying at least one of the impressed potentials in accordance with variations of a modulating signal magnitude to cause corresponding phase modulated currents in said circuits, and a push-pull amplifier having its input controlled by both said resonant circuits to secure a resultant amplitude modulated current in the output thereof.

8. In combination, a pair of resonant circuits,

tuned to substantially the same carrier frequency, means for impressing carrier frequency potential components upon said circuits, a coupling element interconnecting said circuits, the non-reactive impedances of said circuits being substantially' equal to one another and .to the mutual coupling impedance between the circuits, means for modulatingthe relative amplitude of the potentials impressed upon said circuits in accordance with a modulating signal by currents substantially equal to but in phase quadrature with each other, and means for utilizing the current developed in either of said resonant circuits.

' 9; A phase modulator comprising a pair of inductance coils arranged in fixed relation to each other, a tuning condenser connected across each of said coils to form a pair of resonant circuits tuned to substantially the same frequency, said resonant circuits being arranged in mutual coupling relation, the non-reactive impedances of said resonant circuits being substantially equal toone another andto the coupling impedance between the circuits, means for impressing upon said circuits carrier potentials of .resonant frequency having a predetermined amplitude relation to produce currents in said circuits having a time phase, relation substantially in accordance with said arnplitude relation.

10. A modulator comprising apair of inductance coils, tuning condensers connected across said coils to form a pair of resonant circuits tuned to a predetermined carrier frequency, said circuits being inductively coupled, the non reactive impedances of said circuits being substantially equal to one another and to'the mutual inductive impedance therebetween, means for impressing carrier potentals of predetermined amplitude relation upon said circuits to produce currents therein of substantially equal cuits tunedto a predetermined carrier frequency,

'said circuits being inductively coupled with each other, the non-reactive impedances of said cirinductive relation with said first mentioned inductance coils, means to impress a carrier potential through said third coil upon said first mentioned coils, and further means for oppositely varying the inductive coupling relation of said first coils with respect to said third coil in accordance with variations" of a modulating signal magnitude. u

12 In combination, .a pair of resonant circuits tuned to substantially the same frequency, means for impressing potentials of resonant frequency upon said circuits, reactive coupling means arranged to efl'ect a mutual interchange of resonant energy between said circuits, said coupling means being adapted to produce a predetermined normal phase relation between the currents in said circuits when the potentials impressed thereon are of predetermined relative magnitude, further means for varying the relative magnitude of the potentials impressed upon said circuits, and

a utilization circuit connected to at least one of said resonant circuits.

13. In combination, a pair of resonant circuits tuned to substantially the same frequency, means for impressing potentials of resonant frequency for preventing reaction from said utilization circuit upon said coupling means.

14. In combination, a pair of resonant circuits, each comprising inductance means shunted by a condenser and tuned to substantially the same frequency, means for impressing potentials of resonant frequency upon said circuits, portions of said inductance means being in inductive coupling relation to efi'ect a mutual interchange of resonant energy between said circuits, the eifective coupling between said, circuits being adapted to produce a predetermined normal relation 'between the currents in said circuits developed by impressed potentials of predetermined relative magnitude, means for varying the relative magnitude of the impressed potentials to correspondingly vary the relative phase of said currents in respect to their normal phase relation, and a said resonant circuits.

15. In combination, a pair of resonant circuits comprising substantially equal inductance means shunted by equal condensers, means. for normally impressing a potential of resonant frequency upon atleast one of said circuits, portions of the inductance mean-s of said circuits being in coupling relation to efiect a mutual interchange of resonant energy between said circuits, the effective mutual coupling being adapted to produce a preedtermined normalv phase relation of the currents developed in said circuits by the impressed potentials of predetermined relative magnitude, and further means for irnpressing additional potentials upon at least one of said circuits to correspondingly vary the relative means being adapted to effect a predetermined normal phase relation between the currents in said circuits developed'by impressed potentials of predetermined relative magnitudes, means for impressing an unmodulated component of said carrier oscillation upon oneof said circuits, and further means for impressing said modulated carrier-suppressed component upon said other 'resonant circuit.

17. In a phase modulation system, a source of carrier oscillations, a pair of resonant circuits tuned t9 the carrier frequency, reactive coupling means interconnecting said resonant circuits to eifect a mutual interchange of resonant energy therebetween, means for deriving a carrier potential from said source and for impressing the same upon one of said circuits, means for independently deriving a further carrier potential from said source, means for amplitude modulating said latter carrier potential in accordance with variations of a signal magnitude, and further means for impressing the modulated component of said latter carrier potential upon said other resonant circuit, an output circuit differentially coupled to both said resonant circuits, and means to prevent reaction from said output circuit upon said coupling means.

18. A phase modulator comprising a pair of resonant circuits, each comprising an inductance coil, said inductance coils arranged in fixed relation relative to each other, a third inductance coil arranged in inductive coupling relation to both said first inductance coils, reactive coupling means interconnecting said resonant circuits to efiect a mutual interchange of resonant energy therebetween, said coupling meansbeing adapted to produce a predetermined normal phase relation between the currents in said resonant circuit caused by impressed potentials of predetermined relative magnitude, means for impressing a resonant carrier potential upon said third inductance coil, a mechanical translating device, and meansfor translating the movements of said device into relative movements between said pair of fixed inductance coils and said third inductance coil.

19. In combination, a source of high frequency energy, a pair of mutually fixed coils movably arranged in a high frequency field provided by said source, condensers connected to said coils to form resonant circuits tuned to the frequency of said source, reactive coupling means between said circuit adapted to effect a mutual interchange of resonant energy therebetween to produce a normal phase shift between the currents in said circuits at a predetermined position of said coils in said high frequency field, actuating means for displacing said coils relative to said predetermined position, an

amplifier connected to at least one of said resonant circuits, and a utilization connected to the output of said amplifier.

20. In a combination, a source of high frequency energy, a pair of mutually perpendicular coils arranged rotatably about a common axis in a high frequency field provided by said source, condensers connected to said coils to form resonant circuits tuned to the frequency of said source, reactive coupling means between said circuits adapted to effect a mutual interchange of resonant energy therebetween to produce a normal predetermined phase shift between the currents in said resonant circuits at a predetermined position of said coils in said high frequency field, actuating means for oscillating said coils in accordance with a varying magnitude to be translated, an amplifier connected to at least one of said resonant circuits, and a utiliza- 21. In combination, a source of high frequency energy, a pair of induction coils fixed relative to each other and arranged to be movable in unison in a high frequency field provided by said source, condensers connected to said coils to form resonant circuits tuned to the frequency of said source, reactive coupling means betweensaid resonant circuits adapted to effect a normal predetermined'phase shift between the currents in said circuits at a predetermined position of said coils in said high frequency field, means for actuating said coils to differentially vary the magnetic fiux therethrough by said high frequency field to cause corresponding phase modulation of the currents in said resonant circuits, amplifiers connected to said resonant circuits, and a common utilization circuit fed by the output. of both said amplifiers to produce amplitude modulated energy therein. I

22. In combination a source of high frequency energy, a pair of crossed induction coils rotatably arranged about a common axis in a high frequency field provided by .said source, condensers connected to said coils to form resonant circuits tuned to the frequency of said source, inductive coupling means between said circuits adapted to effect a normal predetermined phase shift between the currents in said resonant circuits at a predetermined position of said coils in said high frequency field, means for oscillating said coils in vary the magnetic flux therethrough provided by said high frequency field to cause corresponding differential phase modulation of J OZEF PLEBANSKI.

- tion circuit connected to the output of said 

